1. Field of the Invention
The present invention relates to a circuit substrate manufacturing method and, more particularly, a circuit substrate manufacturing method applicable to a package substrate of electronic parts.
2. Description of the Related Art
As the method of manufacturing the circuit substrate into which electronic parts are packaged, in Patent Literature 1 (Patent Application Publication (KOKAI) 2000-323613), there is set forth the method of manufacturing the circuit substrate by forming the predetermined build-up multi-layered wiring on one surface of the copper plate, and then removing selectively the copper plate. Also, in Patent Literature 2 (Patent Application Publication (KOKAI) 2003-142617), there is set forth the method of manufacturing the circuit substrate by pasting two sheets of copper plate together via the adhesive applied to their peripheral portions, then forming the predetermined build-up multi-layered wiring on both surfaces respectively, then separating their peripheral portions of the copper plate from the main body of the copper plate to separate two sheets of copper plate, and then removing selectively the copper plates respectively.
In addition, in Patent Literature 3 (Patent Application Publication (KOKAI) 2002-83893), there is set forth the method of manufacturing the circuit substrate, from which wirings to which the semiconductor elements are connected are exposed, by forming the predetermined build-up multi-layered wiring on both surfaces of the metal bases respectively, then cutting the metal bases along a surface that is in parallel to the surfaces to separate the metal bases into two parts, and then removing partially respective metal bases.
However, according to the manufacturing methods in connection with Patent Literatures 1 to 3, since the relatively heavy copper plate is used as the substrate, various troubles are caused readily in the manufacturing steps. For example, according to the manufacturing method in connection with Patent Literature 2, since two sheets of copper plate each having an area of 50×50 cm2 and a thickness of 0.4 mm are used, its weight becomes heavy such as about 1.8 kg when two sheets of copper plate are pasted together. Therefore, the workability in handling the copper plate is wrong and also the heavy copper plate must be carried in the manufacturing steps, and as a result the trouble is easily caused in the conveyer system.
Also, it is preferable that, since the copper plate is removed finally, its thickness should be made thin. However, if its thickness is too small, its elasticity and its rigidity are weakened and thus the troubles such as generation of the crack in carrying, etc, are caused. On the contrary, if its thickness of the copper plate is made thick, an amount etched in removing the copper plate is increase and an increase in cost is brought about.
In addition, according to the manufacturing method in connection with Patent Literature 2, the peripheral portions (e.g., almost 3 cm), onto which the adhesive is applied, out of two sheets of copper plate are destroyed as the so-called margin for pasting. Therefore, the overall copper plate cannot be effectively utilized and thus the case where such method becomes disadvantageous in the productivity is assumed.